Finding a Firm Footing
May 28, 2009
The significance of Port Arthur, Texas, is not lost on most professionals in the petroleum industry. Indeed, the Port Arthur Refinery (PAR), owned and operated by Houston-based Motiva Enterprises, is credited with ushering in the country’s modern-day oil industry and giving corporate life to some of today’s largest petroleum companies. More than 100 years later, PAR’s significance is set to take center stage once again thanks to an epic expansion project. The expansion will more than double Port Arthur’s processing capacity to 600,000 barrels a day making it the largest refinery in the United States and one of the top 10 in the world.
San Francisco-based Bechtel Corp., a global engineering, construction and project management company, in a joint venture with Jacobs Engineering Group, headquartered in Pasadena, Calif., is designing and constructing PAR’s expansion--the largest U.S. refinery expansion project ever for Bechtel. Within the refinery’s existing 3,500-acre complex, Bechtel teams are building nine new units and associated structures including a crude distillation unit, a three-unit processing complex, a sulfur recovery facility, a hydrocracker, a hydrotreater, a coker and a power station. The amount of material and equipment required to achieve Motiva’s objectives totals thousands of concrete piles, slabs and vessels, tons of steel and millions of feet of pipe and cable--not a bolt of which is being placed without precise survey measurements and control.
These exacting requirements have kept Bechtel surveyors constantly busy and extremely challenged. “The significant amount of construction activities around the site coupled with the heavy equipment traffic causes ground movement, so it has been a real challenge to establish and maintain consistent control,” says Doug Wooley, Bechtel’s lead project surveyor. “At times, the amount of equipment on site has also limited our ability to see targets to shoot control, and the vastness of the project site has required us to devise very efficient and effective management strategies to juggle the workloads and 23 different field crews.”
To help counter these challenges, surveyors have enlisted their own hefty inventory of advanced survey equipment--tools that Wooley says have given them the firm footing they need to roll with the changes from the ground up. “We have more survey technology on this project than most survey companies have in their entire inventory,” Wooley says. “We have 16 Trimble S6 total stations alone. And we use every one of them nearly every day. The equipment really helps bring this massive jobsite down to a manageable size and enables us to be very responsive to whatever surprises the project presents us--whether it’s the ground shifting, design changes or revising work priorities. That adaptability has been key for us to consistently deliver quality measurements and stay on schedule.”
Controlling the Control
Survey crews arrived on the 11,000-by-8,000-foot site in July 2007 and immediately set out to establish a control network and construction perimeter for each of the new units using a Trimble NetR5 GPS Base Station and five Trimble R8 GNSS receivers. By August, the crew had a unified coordinate system in place and were able to begin the daily ritual of delegating work assignments, performing layouts and setting control points, verifying field work, pouring concrete, performing as-built surveys and updating the design and fieldwork data.
However, two months into preparing the property for above-ground construction, they realized that some areas of their work site were experiencing ground-surface movement due to the forceful pounding of up to 10 piling rigs. To support so many new units and associated structures, field crews had to stakeout and drive 60,000 roughly 80-foot-long piles into the ground--an action that in a few locations caused piles within 10 feet of each other to shift and forced the impacted soil to heave significantly. Within the first week of driving piles, a two-person “verification” crew using the Trimble R8 discovered that the ground heave was causing the existing ground control to become as shaky as the ground itself.
“Very early in setting the foundation piles we realized that as a crew would drive in a second line of piles, the ground heave would push the first line over by several inches,” Wooley says. “That land displacement was shifting our established control inside the construction areas by as much as several inches. So we had to devise a new control strategy to maintain a stable and accurate control network.”
Wooley and his crews needed to first reestablish control across all of the individual construction zones. Bechtel crews adopted a resection approach using the Trimble S6 and the Trimble TSC2 Survey Controller. Teams set several sticky targets on existing structures outside the individual construction areas such as pipe rack columns and buildings. Using the S6’s direct reflex (DR) technology, which allows surveyors to take measurements from a distance without a prism, crews shot the series of targets, and the TSC2 calculated the instrument’s exact location enabling them to set control inside the construction perimeters. The reestablished control grid was then saved in the controller allowing surveyors to simply reference that grid to both verify and reestablish control, if necessary, across the entire work site.
Bechtel’s two verification crews, who are responsible for verifying survey work and establishing control, then began weekly checks of the existing control within each construction zone using the Trimble S8 Total Station--a monitoring routine that still continues today. If any inaccuracies are detected, the crews follow the same resection approach and establish new control points.
“Without the reflectorless capabilities of the total station, setting control would be much more time consuming and cumbersome,” Wooley says. “We would have to set up a conventional backsight using a tripod and a tribrach mounted with a prism and then manually shoot each point. The reflectorless technology erases all that effort and lets us simply set up the instrument [and] select a known control point, and it automatically shoots our existing sticky targets for our resection. It was much quicker and more accurate--the S6 and S8 can measure targets to within thousandths of a foot horizontally and vertically.”
Once alerted to the soil sensitivity, Bechtel teams increased their monitoring regime using the triad of Trimble instruments--the Trimble R8 GNSS, Trimble S8 and Trimble S6--to maintain the quality, accuracy and integrity of the new structures being built throughout the site. For example, surveyors used the R8 GNSS receivers daily on the piles to ensure the foundations stayed within the construction tolerances of 6 inches horizontal and 2 inches vertical. When teams needed to excavate a 30-foot hole to lay the concrete foundation for the new coker unit, the survey crew used the Trimble S8 to set control for the excavation, monitored ground movement surrounding the dig site, set control again within the pit, and then checked for any movement while crews drove sheet piling around the sides and laid the concrete foundation. And when crews were ready to begin erecting structural steel, surveyors began regularly using both the Trimble S6 and S8 to monitor workers’ progress and ensure all elements were positioned correctly.
Sweating the Small Stuff
Indeed, since the majority of the new units have reached the above-ground construction phase, Wooley says the crews have been able to appreciate the fruits of their measuring labor. However, they continue to deploy their entire inventory of total stations and survey controllers, including 20 Trimble TSC2 units, nearly every day.
“We have needed--and continue to need--an astounding amount of material to build all these new structures, and it’s all prefabricated,” Wooley says. “So we need to be extremely precise in our measurements to ensure all the pieces will fit properly when they arrive on site. Bolts, for example, need to be within one-eighth inch or none of the prefabricated steel will connect. To date, all of our construction pieces have fit. And that’s in large part due to the precision of the Trimble technology.”
In fact, bolts have been one of the most critical elements on the PAR expansion. With more than 50,000 tons of structural steel required for construction, Wooley and his survey crews have needed to lay out thousands of bolt patterns. Performing that essential work without advanced survey equipment would have “absolutely consumed” field teams and greatly increased the potential for miscalculating control points to set the bolt line, Wooley says.
“With the S6, we can lay out bolt patterns by simply inputting into the controller the point number for a specific bolt and the instrument automatically turns to where it should be,” Wooley says. “Without that feature, we would have to turn specific angles manually and manually input the calculations to lay the features out. That is not only really laborious, it leaves a lot of room for human error.”
Reducing the potential for human error has been particularly important for this project given the large number of workers employed at the site, 37 of whom are professional surveyors with varying degrees of field experience. That diversity provided Bechtel with the opportunity to capitalize on the Trimble S6’s inherent robotic functionality, which Wooley says not only enabled crews to work very efficiently in the field but also offered party chiefs the ability to train surveyors in real time while still maintaining stringent accuracy and timeline requirements.
“Using the S6 as a robotic total station allows the party chief and the rodman to work side by side on assignments rather than the typical scenario of one person standing behind the instrument and the other person being 200 feet away,” Wooley explains. “Giving the party chief the ability to work side by side with surveyors allows him to have a better view of field operations. And if he has a more inexperienced rodman with him, it allows him to do hands-on training with the rodman at his side rather than trying to tell him what to do from a distance.”
Additional efficiency is gained through the TSC2 survey controllers, which provide the teams with desktop computer functionality in the field so that they can do calculations, quickly reference any control grid and update any field work. Wooley says that the firm is also using the controller as a GIS tool for the first time. “We import a background map of the work site onto the device to give surveyors a spatial view of points rather than just a list of points,” he says. “That really enhances teams’ awareness and efficiency because they have all the data they need at their fingertips.”
Indeed, the controllers serve as an essential wireless connector joining all the Trimble GNSS and total station instruments as well as field teams in real time through one data hub and one data interface. Since the system is integrated with Trimble Geomatics Office and Terramodel software, personnel can generate contour drawings or point reports and update fieldwork progress and then upload the relevant data files to the controllers to ensure teams are working with the most up-to-date information available. The ability to monitor all the different operations through the data collectors helps supervisors better direct site tasks and stay connected to all the various pockets of work areas.
As construction continues on the soon-to-be largest U.S. refinery, that connectedness has been--and continues to be--a critical enabler to help keep Bechtel teams firmly grounded.
Sidebar: Plans for PARThough Port Arthur Refinery (PAR) officially began in November 1903 as the first refinery of Texas Fuel Co. (now Texaco, a subsidiary of Chevron Products Co.), its true beginning actually dates back to January 10, 1901--the day a huge gusher called the “Lucas Gusher” or “Spindletop” came in just south of Beaumont and marked the birth date of the modern petroleum industry. At 100,000 barrels of oil a day, the gusher tripled United States oil production overnight.
For the next 100 years, PAR not only increased its crude capacity but also expanded its processing capabilities to include aviation fuel, gasoline, distillates and lubricant oils. Today, PAR produces 275,000 barrels of crude-based products per day. But as much as PAR has expanded its crude processing facilities, it still has not been enough to satisfy demand. “The last time a major refinery was built in this country was about 30 years ago,” said William Welte, Motiva’s then-president and CEO, at the expansion groundbreaking ceremony in October 2007. “We import over a million barrels of gasoline every day in this country because we don’t have enough gasoline and diesel fuels in the U.S.”
Motiva executives saw PAR as the opportunity to help energize the domestic supply chain. According to Welte, PAR’s strategic Gulf Coast location, with its inherent access to tanker-borne crude oil and major product pipelines, made it an ideal choice for the greatly needed expansion. Upon the project’s completion in 2011, PAR will nearly double its crude oil capacity to to 600,000 barrels a day, increase its transportation fuels output to 23 million gallons a day and transform the facility into the largest sulfur producer in the country.
Sidebar: PAR Project in Numbers:• 60,000 piles totaling more than 4 million feet--nearly the width of Texas
• 2.7 million feet of pipe--the distance from Port Arthur to Panama City, Fla.
• 5.6 million feet of cable--the distance from Port Arthur to the southern edge of Chicago
• 70,000 tons of structural steel--equivalent to the weight of the Queen Elizabeth 2 (QE2) cruise ship
• 310,000 cubic yards of concrete--the equivalent of 31,000 standard truckloads of concrete